This invention relates to a multiple function plate tumbler-type cylinder lock mechanism. More particularly, the invention relates to a lock mechanism which is operated by three or more keys to perform an equal number of functions.
Cash registers and other enclosures frequently are secured by a lock mechanism which is supplied with two keys for use alternatively to perform one of two functions, depending on which key is used. Thus, for example, the operation of a cash register may be controlled by an electrical switch operated by a lock mechanism. One key may be supplied to a teller, such key being inserted in the lock mechanism and turned in one direction or the other and to the extent necessary for providing limited access to the cash register. A second key may be supplied to a supervisor, and such key may be turned in an appropriate direction and to an appropriate extent for providing greater access to the register.
A demand exists for an acceptable lock mechanism which will perform more than two functions, by operation with a corresponding number of different keys. As an example, in addition to performing the above-described functions, it may be desirable that the lock mechanism be operable to provide an additional type of access to an auditor. It may be desirable also that such access be given while retaining the key captive in the lock mechanism, i.e., not removable, to minimize the possibility that the mechanism will be left in a condition allowing access to the register.